The present invention relates to a sheet finisher having a stapler to conduct a staple processing on sheets after the image formation, and an image forming apparatus having the sheet finisher.
The finisher in which, after the image formation is conducted on the sheet, a bundle of a plurality of sheets is stapled, is fitted to the image forming apparatus as a standard function of the high speed image forming apparatus by which an image is formed by the electro-photographic method.
A stapler generally composed of a stacking means for stacking the sheets conveyed in the finisher one by one sheet after the image formation, by the preset number of sheets, and a stapling means for stapling the stacked sheets by staples. In the continuous image forming process, the image formed sheet conveyed-in from the image forming apparatus main body is conveyed in the sheet finisher at a predetermined sheet interval. In the stapler, however, it is necessary that a comparatively long sheet interval is taken between the bundles of the sheets to be stapled, and because the sheet interval between the sheet bundles is longer than the sheet interval between the sheets to be conveyed in, it is necessary to have an adjustment between the conveying control of the sheet in the image forming apparatus main body and the conveying control in the sheet finisher.
As the image formation speed is increased, the mismatching as described above between the sheet interval of the sheet to be conveyed-in from the image forming apparatus main body and the sheet interval of the sheet which can be received by the stapler becomes a problem, thereby a case in which the high speed performance of the image forming apparatus main body is sacrificed to some extent and the productivity of the image formation is necessarily lowered, is generated.
As a countermeasure for such a problem, in Japanese Tokkaihei No. 1-127556, a sheet finisher in which conveying paths of two long and short system are provided upstream the stacking means and the top sheet after the second bundle of the sheet bundles to be stapled, is conveyed in the stacking means through the long conveying path, and the other sheets are conveyed in the stacking means through the short conveying path, is proposed.
Further, in Japanese Tokkaihei No. 9-235069, a sheet finisher in which a sheet stand-by section for making standby two sheets is provided, is proposed.
In the sheet finisher in Japanese Tokkaihei No. 1-127556, because the exclusive use long conveying path for delaying the conveying timing to the stacking means is provided, there is a problem that the image forming speed is high speed, and as the difference between the conveying-in speed of the sheet from the image forming apparatus and the processing speed of the stapler is increased, the length of the conveying path is increased, and the apparatus size is increased. Further, when the long conveying path is arranged in a small sized finisher, the shape of the conveying path becomes complex, and it is difficult that the stable conveying property is secured. As described above, although the sheet finisher in Japanese Tokkaihei No. 1-127556 aims the high speed image formation, the problem becomes conspicuous in the high speed area.
In the sheet finisher in the Japanese Tokkaihei No. 9-235069, because the stand by section for the sheet is provided in the conveying path by which the sheet is conveyed in the stacking means, it is required that the conveying path has both conveying function and accommodation function together, and there is a problem that, for the sheets ranging from the large size to the small size, it is difficult that these requirements are satisfied.
An object of the present invention is to solve the above described problem relating to the mismatching between the image forming speed of the image forming apparatus main body and the processing speed of the stapler.
The object of the present invention is attained by any one of Structures (1)-(8).
(1) A sheet finisher which has a stacking means for stacking a sheet conveyed-in from an image forming apparatus and a stapling means for stapling the stacked sheets, the sheet finisher is characterized in that: it has a conveying timing adjustment section arranged upstream of the stacking means, and the conveying timing adjustment section has; a conveying-in section; a conveying-out section separately provided from the conveying-in section; a reversal conveying section to reverse the conveying direction of the sheet conveyed from the conveying-in section in one direction and to convey-out it from the conveying-out section; and a control means for conducting the control of the reversal conveying section, wherein the control means controls the reversal conveying section such that at least a second bundle or a bundle after the second bundle of the sheet bundles to be stapled by the stapler, in which a plurality f sheets having at least a top sheet and a succeeding sheet to the top sheet are overlapped each other, is conveyed-out from the reversal conveying section.
(2) A sheet finisher according to the Structure (1), wherein the reversal conveying section has a sheet accommodation section vertically arranged for accommodating the sheet conveyed-in and a stopping member for stopping the sheet conveyed-in, wherein the control means controls the stopping member to send out the sheet to the conveying-out section after stopping the sheet conveyed-in the sheet accommodation section.
(3) A sheet finisher according to either one of the Structure (1) or the Structure (2), wherein the control means controls the reversal conveying section such that the bundle having at least the top sheet and a sheet succeeding to the top sheet which are overlapped each other in the reversal conveying section, and remaining sheets other than the top and the succeeding sheets of said second bundle and sheets of a preceding first bundle is conveyed-out one by one from the reversal conveying section.
(4) A sheet finisher according to any one of the Structures (1)-(3), wherein the reversal conveying section is arranged in the vicinity of the sheet conveying-in inlet of the sheet finisher.
(5) A sheet finisher according to any one of the Structures (1)-(4), wherein the stapling means staples at edge or center position of the sheets.
(6) A sheet finisher according to any one of the Structures (1)-(5), wherein it has an alignment means.
(7) A sheet finisher according to any one of the Structures (1)-(6), wherein it has a folding section.
(8) An image forming apparatus characterized in that: it has the sheet finisher described in any one of Structures (1)-(7), and an image forming apparatus main body by which an image is formed on the sheet and the sheet is conveyed into the sheet finisher.